1. Field of the Invention
This invention relates, in general, to hydraulic couplings, and specifically to hydraulic couplings used in undersea drilling and production applications. More particularly, the invention involves seals between male and the female coupling members in undersea hydraulic couplings.
2. Description of Related Art
Subsea hydraulic couplings are old in the art. The couplings generally consist of a male member and a female member with seals to seal the junction between the male and female members. The female member generally has a cylindrical body with a relatively large diameter bore at one end and a relatively small diameter bore at the other. The small bore facilitates connections to hydraulic lines, while the large bore contains the seals and receives the male portion of the coupling. The male member includes a probe section insertable into the large bore of the female member. According to various embodiments of the device, the seals either abut the end, or face, of the male member or engage the male member about its outer circumference. Hydraulic fluid is then free to flow through the female and male portions of the coupling and seals prevent that flow from escaping about the joints of the coupling.
Optionally, a check valve may be installed in the female member and also in the male member. Each check valve is open when the coupling is made up; however, each check valve closes when the coupling is broken so as to prevent fluid from leaking out of the system of which the coupling is part.
In U.S. Pat. Nos. 4,694,859 and 5,762,106 to Robert E. Smith III, an undersea hydraulic coupling and metal seal is disclosed. A reusable metal seal engages the circumference of the probe when it is positioned within the female member body. The seal is held in place by a cylindrical seal retainer. When the male and female portions of the coupling are parted under pressure, the seal retainer prevents the metal seal from blowing out through the bore of the female member.
In U.S. Pat. No. 5,339,861, a hydraulic coupling with a hollow metal O-ring seal is disclosed. The hollow metal O-ring is held captive between an internal shoulder and a retainer inserted into the internal bore of the female member. The metal O-ring also may be pressure-energized to expand the seal cavity in response to fluid pressure in the coupling.
To retain the metal seal in the female member of an undersea hydraulic coupling, a seal retainer may be connected to the female member. The seal retainer may be a generally sleeve-shaped cylindrical body that is inserted into the bore of the female member until the seal retainer abuts a shoulder in the bore of female member. To secure the seal retainer against the shoulder, a retainer locking member may also be attached to the female member using threads or snap rings, for example.
Although metal seals that are used in undersea hydraulic couplings are generally reliable, a leak path may exist between the seal retainer and the female coupling member. In the past, elastomeric O-rings have been used to provide a seal between the outer circumference of the seal retainer and the inner circumference of the bore of the female coupling member. However, the elastomeric O-rings may not be reliable enough to block this leak path at the extreme temperatures and pressures that may be encountered at subsea depths. A more reliable seal is needed between the seal retainer and female coupling member to withstand the temperatures and pressures in the subsea environment. An undersea hydraulic coupling is needed having a more reliable seal around the outer circumference of the seal retainer that may be removed and replaced.